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Config option {merge_strategy, fast|predictable}

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Both options have same log2(N) upper bound on
latencies, but `fast' fluctuates.
This commit is contained in:
Kresten Krab Thorup 2012-05-01 16:27:06 +02:00
parent 01ea88b67c
commit c8964e955c
2 changed files with 21 additions and 6 deletions
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13
README.md
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@ -38,9 +38,16 @@ Put these values in your `app.config` in the `hanoi` section
{data_root, "./data/hanoi"},
{compress, none | snappy | gzip},
{sync_strategy, none | sync | {seconds, N}},
{page_size, 8192}
{write_buffer_size, 524288} % 512kB
{read_buffer_size, 524288} % 512kB
{page_size, 8192},
{write_buffer_size, 524288}, % 512kB
{read_buffer_size, 524288}, % 512kB
%%
%% The merge strategy is one of `fast' or `predictable'.
%% Both have same log2(N) worst case, but `fast' is
%% sometimes faster; yielding latency fluctuations.
%%
{merge_strategy, fast | predictable}
]},
```

14
src/hanoi_level.erl
View file

@ -514,7 +514,7 @@ main_loop(State = #state{ next=Next }) ->
{ok, PID} = ?MODULE:open(State#state.dir, State#state.level + 1, undefined,
State#state.opts, State#state.owner ),
State#state.owner ! { bottom_level, State#state.level + 1 },
State#state{ next=PID };
State#state{ next=PID, max_level= State#state.level+1 };
true ->
State
end,
@ -582,10 +582,18 @@ do_step(StepFrom, PreviousWork, State) ->
true ->
WorkLeftHere = 0
end,
WorkUnit = ?BTREE_SIZE(?TOP_LEVEL),
MaxLevel = max(State#state.max_level, State#state.level),
TotalWork = (MaxLevel-?TOP_LEVEL+1) * ?BTREE_SIZE(?TOP_LEVEL),
TotalWork = (MaxLevel-?TOP_LEVEL+1) * WorkUnit,
WorkUnitsLeft = max(0, TotalWork-PreviousWork),
WorkToDoHere = min(WorkLeftHere, WorkUnitsLeft),
case hanoi:get_opt( merge_strategy, State#state.opts, predictable) of
fast ->
WorkToDoHere = min(WorkLeftHere, WorkUnitsLeft);
predictable ->
WorkToDoHere = min(WorkLeftHere, WorkUnit)
end,
WorkIncludingHere = PreviousWork + WorkToDoHere,
?log("do_step prev:~p, do:~p of ~p ~n", [PreviousWork, WorkToDoHere, WorkLeftHere]),